Parking brake apparatus for vehicle

ABSTRACT

A parking brake apparatus for a vehicle includes a driving unit including a plurality of motor sections; a pair of pressing units receiving power from the driving unit and pressing a brake pad; and a load transmission unit installed between the pair of pressing units, connected to each of the pair of pressing units, and transmitting a pressing load of any one of the pair of pressing units to the other pressing unit.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority from and the benefit of Korean PatentApplication No. 10-2019-0086031, filed on Jul. 16, 2019, which is herebyincorporated by reference for all purposes as if set forth herein.

BACKGROUND Field

Exemplary embodiments of the present disclosure relate to a parkingbrake apparatus for a vehicle, and more particularly, to a parking brakeapparatus for a vehicle capable of uniformly transmitting loads to abrake pad.

Discussion of the Background

In general, an actuator of an electronic parking brake for a vehicle isconstructed by a motor and a power transmission device for operatingfriction pads installed in a caliper of a disc brake apparatus whenparking.

When a driver pushes a parking brake switch, the rotational force of amotor of the actuator is transmitted to an input shaft of the caliperthrough the power transmission device such as a reduction gear. Throughthe rotation of the input shaft, a pressure connection sleeve is movedforward, and by the forward movement of the pressure connection sleeve,a piston which accommodates the pressure connection sleeve and a caliperhousing are moved toward each other, such that two friction pads mountedto the piston and the caliper housing are pressed against both surfacesof a disc to restrain the rotation of the disc.

In the case where a plurality of pistons are provided and receive adriving force from a single actuator, loads may be non-uniformlytransmitted to the plurality of pistons. In this case, uneven wear offriction pads may be caused, and the braking performance may bedegraded.

SUMMARY

Various embodiments are directed to a parking brake apparatus for avehicle capable of uniformly transmitting loads to a brake pad by a loadtransmission unit.

In an embodiment, a parking brake apparatus for a vehicle may include: adriving unit including a plurality of motor sections; a pair of pressingunits receiving power from the driving unit and pressing a brake pad;and a load transmission unit installed between the pair of pressingunits, connected to each of the pair of pressing units, and transmittinga pressing load of any one of the pair of pressing units to the otherpressing unit.

Each of the pair of pressing units may include: a sun gear sectionrotated by receiving power from the driving unit; a planetary gearsection rotated by being meshed with the sun gear section; a carriersection coupled to the planetary gear section; and a piston sectionconnected to the carrier section, and pressing the brake pad by beingmoved toward the brake pad through receiving rotational power from theplanetary gear section.

The pair of pressing units may individually receive power from theplurality of motor sections, respectively.

Any one of the pair of pressing units may receive power by beingconnected with some of the plurality of motor sections, and the otherone of the pair of pressing units may receive power by being connectedwith the other some of the plurality of motor sections.

The load transmission unit may include a pair of ring gear sections,each of the pair of ring gear sections may be rotatable by being meshedwith the planetary gear section, and the pair of ring gear sections maybe directly or indirectly meshed with each other.

Each of the pair of ring gear sections may include: a ring gear innerpart formed with an internal gear portion on an inner circumferentialsurface thereof to be meshed with the planetary gear section; and a ringgear outer part coupled to an outer surface of the ring gear inner part,and formed with an external gear portion on an outer circumferentialsurface thereof to be meshed with the other ring gear sectionneighboring thereon.

The ring gear inner part and the ring gear outer part may be integrallyformed.

The ring gear inner part may project more toward the sun gear sectionthan the ring gear outer part, and may surround the sun gear section andthe planetary gear section.

The carrier section may be spline-coupled to the piston section.

The piston section may receive rotational power from the carriersection, and may be linearly reciprocated relative to the brake paddepending on a rotating direction of the carrier section.

The sun gear section may be dynamically connected to the driving unitthrough a connection gear section.

The sun gear section may include: a sun gear connection body coupled tothe connection gear section; and a sun gear formed on the sun gearconnection body, having a rotation center that is concentric with arotation center of the connection gear section, and meshed with theplanetary gear section.

In the parking brake apparatus for a vehicle according to the presentdisclosure, when a pressing load is concentrated on any one of aplurality of pressing units, a load transmission unit may transmit thepressing load to the remaining pressing unit, so that the pressing unitsmay press a brake pad with uniform loads.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view illustrating a parking brake apparatus fora vehicle in accordance with an embodiment of the present disclosure.

FIG. 2 is a partial perspective view illustrating the parking brakeapparatus for a vehicle in accordance with the embodiment of the presentdisclosure.

FIG. 3 is a partial exploded view illustrating the parking brakeapparatus for a vehicle in accordance with the embodiment of the presentdisclosure.

FIG. 4 is a front view illustrating the parking brake apparatus for avehicle in accordance with the embodiment of the present disclosure.

FIGS. 5 to 7 are state views illustrating driving states of the parkingbrake apparatus for a vehicle in accordance with the embodiment of thepresent disclosure.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

Hereinafter, a parking brake apparatus for a vehicle will be describedbelow with reference to the accompanying drawings through variousexamples of embodiments. It should be noted that the drawings are not toprecise scale and may be exaggerated in thickness of lines or sizes ofcomponents for descriptive convenience and clarity only.

Furthermore, the terms used herein are defined by taking functions ofthe invention into account and can be changed according to the intentionof users or operators or the practice. Therefore, definition of theterms should be made according to the overall disclosures set forthherein.

FIG. 1 is a perspective view illustrating a parking brake apparatus fora vehicle in accordance with an embodiment of the present disclosure.FIG. 2 is a partial perspective view illustrating the parking brakeapparatus for a vehicle in accordance with the embodiment of the presentdisclosure. FIG. 3 is a partial exploded view illustrating the parkingbrake apparatus for a vehicle in accordance with the embodiment of thepresent disclosure. FIG. 4 is a front view illustrating the parkingbrake apparatus for a vehicle in accordance with the embodiment of thepresent disclosure. FIGS. 5 to 7 are state views illustrating drivingstates of the parking brake apparatus for a vehicle in accordance withthe embodiment of the present disclosure.

Referring to FIGS. 1 to 5, a parking brake apparatus 1 for a vehicle inaccordance with the embodiment of the present disclosure includes adriving unit 50, pressing units 100 and 200, and a load transmissionunit 300.

The driving unit 50 includes a motor section 60 which receives electricpower from the outside and generates power. The motor section 60includes a motor body 61 which generates power and a driving gear 62which is rotated by the motor body 61.

In the present embodiment, the driving gear 62 is formed in the shape ofa spur gear, but the shape thereof may be replaced with other gearshapes or the likes as long as the driving gear 62 can transmit power tothe pressing units 100 and 200.

The driving unit 50 may further include a power transmission section(not illustrated). That is to say, the motor section 60 of the drivingunit 50 may transmit generated power directly to the pressing units 100and 200, or may transmit generated power to the pressing units 100 and200 by the medium of the power transmission section.

In the present embodiment, the driving unit 50 includes two motorsections 60, and separately provides power to each of connection gearsections 120 and 220.

In the present embodiment, since balancing is implemented betweenplanetary gear sections 130 and 230 which will be described later, eventhough power is separately provided to the respective pressing units 100and 200 by using the plurality of motor sections 60, the same loads maybe transmitted to piston sections 170 and 270.

In particular, using a plurality of small-capacity motor sectionsinstead of using a large-capacity motor section to secure the samecapacity may provide advantages in that it is possible to reduce thesize of a brake apparatus and improve the degree of freedom ofinstallation.

Referring to FIGS. 1 to 3, the parking brake apparatus 1 for a vehiclein accordance with the present embodiment includes a mounting case 500and a mounting cover 510.

The driving unit 50, the pressing units 100 and 200 and the loadtransmission unit 300 are disposed in the mounting case 500. Themounting cover 510 is detachably coupled to the mounting case 500, andcloses one side opening of the mounting case 500 to prevent foreignmatters from entering the inside of the mounting case 500.

The pressing units 100 and 200 in accordance with the embodiment of thepresent disclosure are installed in a caliper housing 10, receive powerfrom the driving unit 50, and press a brake pad 20 which is brought intofrictional contact with a disc (not illustrated).

A plurality of pressing units 100 and 200 are provided. The plurality ofpressing units 100 and 200 are disposed side by side. The pressing units100 and 200 are symmetrically installed at left and right sides (in FIG.4) with respect to the center portion of the brake pad 20.

The pressing units 100 and 200 receive power from the driving unit 50,and press the brake pad 20 with the same pressing loads. The brake pad20 is moved toward the disc by such pressing forces, and a braking forceis generated due to the friction between the brake pad 20 and the disc.

The pressing units 100 and 200 in accordance with the embodiment of thepresent disclosure include sun gear sections 110 and 210, the connectiongear sections 120 and 220, the planetary gear sections 130 and 230,carrier sections 150 and 250, and the piston sections 170 and 270.

Meanwhile, in the illustration of FIGS. 4 to 7, the connection gearsections 120 and 220 are omitted for the sake of convenience inexplanation.

The connection gear sections 120 and 220 transmit power, provided fromthe driving unit 50, to the sun gear sections 110 and 210. Theconnection gear sections 120 and 220 are formed in the shapes of spurgears since they are meshed with the driving gears 62, but may bechanged in their shapes depending on changes in the shapes of thedriving gears 62.

The sun gear sections 110 and 210 are rotated by receiving power fromthe driving unit 50. According to the present embodiment, the sun gearsections 110 and 210 are coupled to the connection gear sections 120 and220. The sun gear sections 110 and 210 may be rotated through theconnection gear sections 120 and 220 which are dynamically connected tothe driving unit 50.

The sun gear sections 110 and 210 include sun gears 111 and 211 and sungear connection bodies 112 and 212.

The sun gear connection bodies 112 and 212 are coupled to the connectiongear sections 120 and 220. The sun gears 111 and 211 are formed at thecenter portions of the sun gear connection bodies 112 and 212, and areformed in the shapes of gears on the outer circumferential surfacesthereof to be meshed with the planetary gear sections 130 and 230.

The sun gear sections 110 and 210 are concentric with the rotationcenters of the connection gear sections 120 and 220. Therefore, if thepower of the driving unit 50 is transmitted to the connection gearsections 120 and 220, the connection gear sections 120 and 220 and thesun gear sections 110 and 210 are rotated on the same rotation axes.

The sun gear sections 110 and 210 may be integrally formed with theconnection gear sections 120 and 220. Alternatively, the sun gearsections 110 and 210 may be formed as separate bodies from theconnection gear sections 120 and 220, and may be integrated with theconnection gear sections 120 and 220 through coupling.

As the sun gear sections 110 and 210 are integrally formed with theconnection gear sections 120 and 220 or are integrated with theconnection gear sections 120 and 220, if the connection gear sections120 and 220 are rotated, the sun gear sections 110 and 210 are alsorotated together.

The sun gears 111 and 211 are disposed inside the planetary gearsections 130 and 230, respectively, each of which is provided with aplurality of gears. The planetary gear sections 130 and 230 rotate andrevolve while being meshed with the sun gears 111 and 211.

The planetary gear sections 130 and 230 include a plurality of planetarygears 131 and 231. The present embodiment illustrates that the planetarygears 131 and 231 each are exemplified as four. However, it is to benoted that the present embodiment is not limited thereto, and thus, theplanetary gears 131 and 231 may each be three or less or five or more.

The plurality of planetary gears 131 and 231 are disposed at equalangles about the rotation centers of the sun gears 111 and 211. Theplurality of planetary gears 131 and 231 are meshed with the sun gears111 and 211, and rotate and/or revolve when the sun gears 111 and 211are rotated.

The planetary gear sections 130 and 230 are coupled to the carriersections 150 and 250. In the case where the plurality of planetary gears131 and 231 revolve around the sun gears 111 and 211, the carriersections 150 and 250 are also rotated in a clockwise or counterclockwisedirection (in FIG. 4).

As the carrier sections 150 and 250 are rotated, the piston sections 170and 270 are moved toward the brake pad 20 and press the brake pad 20.

The carrier sections 150 and 250 include carrier bodies 151 and 251,carrier rotation shafts 152 and 252, and carrier connection parts 153and 253.

The carrier rotation shafts 152 and 252 are formed on the carrier bodies151 and 251 to project toward the planetary gear sections 130 and 230.

The carrier rotation shafts 152 and 252 are provided in plural numbersthat are the same as the numbers of the planetary gears 131 and 231 ofthe planetary gear sections 130 and 230, and are coupled through theplanetary gears 131 and 231 of the planetary gear sections 130 and 230.Due to this fact, the planetary gears 131 and 231 of the planetary gearsections 130 and 230 may perform rotating motion while being rotated onthe carrier rotation shafts 152 and 252.

The carrier connection parts 153 and 253 are formed on the innercircumferential surfaces of the carrier bodies 151 and 251, and areconnected to piston connection parts 173 and 273 of the piston sections170 and 270.

In the present embodiment, the carrier connection parts 153 and 253 havegrooves, and the piston connection parts 173 and 273 have protrusionswhich are inserted into the grooves of the carrier connection parts 153and 253.

Alternatively, the piston connection parts 173 and 273 may have grooves,and the carrier connection parts 153 and 253 may have protrusions whichare inserted into the grooves of the piston connection parts 173 and273.

The carrier connection parts 153 and 253 and the piston connection parts173 and 273 may be spline-coupled to each other. Of course, the carriersections 150 and 250 and the piston sections 170 and 270 may be coupledin other ways, for example, screw coupling or the like, in addition tothe spline coupling.

The piston sections 170 and 270 are connected with the carrier sections150 and 250. The piston sections 170 and 270 are rotated together as thecarrier sections 150 and 250 are rotated.

The piston sections 170 and 270 include piston bodies 171 and 271,piston shafts 172 and 272, and the piston connection parts 173 and 273.

The piston bodies 171 and 271 are formed to be internally hollow, andare disposed to be capable of being brought into contact with the brakepad 20 by the movement thereof. The piston bodies 171 and 271 may beformed in cylindrical shapes.

The piston bodies 171 and 271 are coupled with the piston shafts 172 and272, and the piston connection parts 173 and 273 are formed at ends ofthe piston shafts 172 and 272, that is, ends of the piston shafts 172and 272 which face the carrier sections 150 and 250.

When the carrier sections 150 and 250 are rotated, the piston connectionparts 173 and 273 which are spline-coupled to the carrier connectionparts 153 and 253 are rotated, and thereby, the rotational motion of thecarrier sections 150 and 250 is converted into the linear motion of thepiston sections 170 and 270.

Due to the linear movement of the piston sections 170 and 270, thepiston sections 170 and 270 are moved toward the brake pad 20.Therefore, as the piston sections 170 and 270 are brought into contactwith the brake pad 20 and press the brake pad 20, a braking force isgenerated due to the friction between the brake pad 20 and the disc.

The load transmission unit 300 is connected to each of the pair ofpressing units 100 and 200, and transmits a pressing load of any one ofthe pressing units 100 and 200 to the other of the pressing units 100and 200.

The load transmission unit 300 in accordance with the embodiment of thepresent disclosure includes a pair of ring gear sections 310.

The pair of ring gear sections 310 are meshed with the planetary gearsections 130 and 230, respectively, to be able to be rotated thereby.

The pair of ring gear sections 310 may be directly meshed with eachother. That is to say, since the pair of ring gear sections 310 aredirectly connected to each other, power loss in transmitting power ofany one of the pair of ring gear sections 310 to the other may bereduced.

As the pair of ring gear sections 310 are directly meshed with eachother, a space that is occupied by the pressing units 100 and 200 andthe load transmission unit 300 may be reduced.

Alternatively, the pair of ring gear sections 310 may be indirectlymeshed by the medium of at least one transmission gear part (notillustrated). In other words, the transmission gear part may be disposedbetween the pair of ring gear sections 310, and is meshed with the ringgear sections 310 to dynamically connect the pair of ring gear sections310.

Referring to FIGS. 3 to 7, the respective ring gear sections 310 aredisposed outside the planetary gears 131 and 231.

Each ring gear section 310 includes a ring gear inner part 311 and aring gear outer part 315.

The ring gear inner parts 311 are disposed outside the planetary gearsections 130 and 230, and internal gear portions 312 may be formed onthe inner circumferential surfaces of the ring gear inner parts 311 tobe meshed with the planetary gear sections 130 and 230.

The internal gear portion 312 of the ring gear inner part 311 which isinstalled at one side (the left side in FIG. 5) may be meshed with theplanetary gear section 130 to be rotated in the clockwise orcounterclockwise direction (in FIG. 5), and the rotational force thereofmay be transmitted to the ring gear section 310, specifically, the ringgear outer part 315, which is disposed at the other side (the right sidein FIG. 5).

The ring gear outer part 315 is coupled to the outer surface of the ringgear inner part 311, and an external gear portion 316 is formed on theouter circumferential surface of the ring gear outer part 315. The ringgear outer part 315 may be integrally formed with the ring gear innerpart 311.

As the internal gear portion 312 of the ring gear inner part 311 whichis installed at the one side (the left side in FIG. 5) is rotated whilebeing meshed with the planetary gear section 130, the ring gear outerpart 315 which is integrally formed with the ring gear inner part 311 isalso rotated in the same direction.

Therefore, the rotational force of the ring gear outer part 315 at theone side is transmitted to the directly meshed ring gear section 310,specifically, the ring gear outer part 315, which is disposed at theother side (the right side in FIG. 5).

On the other hand, in the case where the transmission gear part isdisposed between the pair of ring gear sections 310, the transmissiongear part is rotated by being meshed with the external gear portions 316which are formed on the ring gear sections 310, specifically, the ringgear outer parts 315, and transmits the rotational power of the ringgear section 310 disposed at the one side to the ring gear section 310disposed at the other side.

The rotational power transmitted to the ring gear section 310 at theother side is transmitted to the carrier section 250 which is coupled tothe planetary gears 231, via the ring gear inner part 311 and theplanetary gears 231. As the planetary gears 231 rotate and revolve onthe outer circumferential surface of the sun gear 211, the carriersection 250 which is coupled to the planetary gears 231 is rotated, andthus, the piston section 270 is moved toward the brake pad 20.

In the case where pressing loads for pressing the brake pad 20 arenon-uniformly applied to the pair of pressing units 100 and 200,specifically, the pair of piston sections 170 and 270, the loadtransmission unit 300 may transmit a pressing load of the piston section170 at the one side to the piston section 270 at the other side suchthat the pair of piston sections 170 and 270 may be brought into contactwith the brake pad 20 with uniform pressing loads.

Of course, conversely, a pressing load of the piston section 270 at theother side may be transmitted to the piston section 170 at the one side.

Referring to FIGS. 4 to 7, the number of the ring gear sections 310 ofthe load transmission unit 300 may be changed. Therefore, the number ofthe ring gear sections 310 is not limited to two as in the presentembodiment, and may be variously changed to one or three or moredepending on a distance between the pair of pressing units 100 and 200.

The operation principle of the parking brake apparatus 1 for a vehicleconstructed as mentioned above will be described below.

In the parking brake apparatus 1 for a vehicle in accordance with theembodiment of the present disclosure, the plurality of pressing units100 and 200 press the brake pad 20 to move the brake pad 20 toward thedisc, and a braking force is generated due to the contact frictionbetween the brake pad 20 and the disc.

In the embodiment of the present disclosure, two pressing units 100 and200 are provided. However, it is to be noted that the present disclosureis not limited thereto, and various modifications in which three or morepressing units are provided are possible.

The pressing units 100 and 200 receive power from the driving unit 50,and are linearly reciprocated relative to the brake pad 20.

In detail, the motor section 60 which individually transmits power isconnected to each of the pressing units 100 and 200. Namely, accordingto the present embodiment, the two motor sections 60 are provided, andany one of the two motor sections 60 transmits power to the pressingunit 100 at the one side and the other of the two motor sections 60transmits power to the pressing unit 200 at the other side.

Even though the two motor sections 60 individually transmit power to thepressing units 100 and 200 at the one side and the other side, thepressing units 100 and 200 include the planetary gear sections 130 and230 in such a manner that balancing is implemented between the planetarygear sections 130 and 230. Thus, it is possible to transmit the sameloads to the pressing units 100 and 200 at both the sides.

By driving the motor sections 60, the respective connection gearsections 120 and 220 which are meshed with the driving gears 62 arerotated.

According to the rotation of the connection gear sections 120 and 220,the sun gear sections 110 and 210 are also rotated in an interlockedmanner, and the planetary gears 131 and 231 which are meshed with thesun gears 111 and 211 perform rotating motion and at the same timeperform revolving motion around the sun gears 111 and 211.

As the planetary gears 131 and 231 perform the revolving motion, thecarrier sections 150 and 250 which are coupled to the planetary gears131 and 231 are rotated in the clockwise or counterclockwise direction.As the carrier sections 150 and 250 are rotated, the piston sections 170and 270 which are coupled to the carrier sections 150 and 250 are movedtoward the brake pad 20 and press the brake pad 20 by being brought intocontact with the brake pad 20.

Due to various factors, the power provided from the driving unit 50 maybe transmitted more to any one of the pair of pressing units 100 and200.

As illustrated in FIG. 6, when driving the parking brake apparatus 1 fora vehicle, in the case where power is applied more to the pressing unit100 disposed at the one side (the left side in FIG. 6) than the pressingunit 200 disposed at the other side (the right side in FIG. 6), thepiston section 170 at the one side may be brought into contact with thebrake pad 20 earlier than the piston section 270 at the other side.

If the piston section 170 at the one side is in a state in which it isalready brought into contact with the brake pad 20 and the pistonsection 270 at the other side is in a state in which it is not yetbrought into contact with the brake pad 20, the planetary gear section130 of the pressing unit 100 at the one side performs only rotatingmotion. That is to say, the planetary gear section 130 does not performrevolving motion.

Since the power generated by the operation of the driving unit 50 iscontinuously transmitted to the sun gear 111, the sun gear 111 iscontinuously rotated. At this time, since the piston section 170 is inthe state in which it is already brought into contact with the brake pad20, the plurality of planetary gears 131 which are meshed with the sungear 111 do not perform revolving operation but perform only rotatingmotion.

Since the pressing unit 100, specifically, the piston section 170, whichis disposed at the left side in FIG. 6 can no longer be moved toward thebrake pad 20, due to a reaction force to this, the planetary gears 131perform only rotating motion, and the ring gear inner part 311 which isformed with the internal gear portion 312 to be meshed with theplanetary gears 131 is rotated in the clockwise or counterclockwisedirection.

The reaction force which is generated in the pressing unit 100 at theone side (the left side in FIG. 6) is transmitted to the pressing unit200 at the other side (the right side in FIG. 6), through the ring gearouter part 315 which is integrally coupled with the ring gear inner part311.

In detail, the power provided to the pressing unit 100 at the one sideis transmitted to the piston section 270 at the other side through theexternal gear portion 316 at the other side, the internal gear portion312 of the ring gear inner part 311, the planetary gear section 230 andthe carrier section 250 coupled with the planetary gear section 230.

Accordingly, the power provided from the driving unit 50 is provided tothe piston section 270 at the other side which is not yet brought intocontact with the brake pad 20, and the linear movement of the pistonsection 170 at the one side which is already brought into contact withthe brake pad 20 is stopped until the piston section 270 at the otherside is brought into contact with the brake pad 20.

Thereafter, when both the piston sections 170 and 270 at the one sideand the other side are brought into contact with the brake pad 20, thepower of the driving unit 50 is provided to the respective pistonsections 170 and 270 at the one side and the other side, and the pistonsections 170 and 270 at the one side and the other side simultaneouslypress the brake pad 20 with uniform loads.

Referring to FIGS. 4 to 7, in the case where a pressing load isconcentrated on the pressing unit 100 at the one side of the pair ofpressing units 100 and 200, the load transmission unit 300 in accordancewith the embodiment of the present disclosure may transmit the pressingload to the pressing unit 200 at the other side such that the pair ofpressing units 100 and 200 may press the brake pad 20 toward the discwith uniform pressing loads.

Likewise, in the case where a pressing load is more concentrated on thepressing unit 200 at the other side of the pair of pressing units 100and 200, the load transmission unit 300 may transmit the pressing loadto the pressing unit 100 at the one side such that the pair of pressingunits 100 and 200 may press the brake pad 20 toward the disc withuniform pressing loads.

Referring to FIG. 3, the ring gear inner parts 311 may project moretoward the sun gear sections 110 and 210 (the left side in FIG. 3) thanthe ring gear outer parts 315. Due to this fact, it is possible toprevent the sun gear sections 110 and 210 from being released from thering gear sections 310 when receiving rotational power from the drivingunit 50.

As the carrier sections 150 and 250 are spline-coupled to the pistonsections 170 and 270, the rotational power of the carrier sections 150and 250 may be transmitted to the piston sections 170 and 270,specifically, the piston connection parts 173 and 273.

The piston connection parts 173 and 273 are coupled to the piston shafts172 and 272 which are coupled to the piston bodies 171 and 271, and, bythe rotational power received through the carrier sections 150 and 250,cause the piston bodies 171 and 271 to be linearly moved toward thebrake pad 20.

Although the disclosure has been disclosed with reference to theembodiments illustrated in the drawings, the embodiments are only forillustrative purposes, and those skilled in the art will appreciate thatvarious modifications and other equivalent embodiments are possible,without departing from the scope and spirit of the disclosure as definedin the accompanying claims. Thus, the true technical scope of thedisclosure should be defined by the following claims.

What is claimed is:
 1. A parking brake apparatus for a vehicle,comprising: a driving unit including a plurality of motor sections; apair of pressing units receiving power from the driving unit andpressing a brake pad; and a load transmission unit installed between thepair of pressing units, connected to each of the pair of pressing units,and transmitting a pressing load of any one of the pair of pressingunits to the other pressing unit.
 2. The parking brake apparatus ofclaim 1, wherein each of the pair of pressing units comprises: a sungear section rotated by receiving power from the driving unit; aplanetary gear section rotated by being meshed with the sun gearsection; a carrier section coupled to the planetary gear section; and apiston section connected to the carrier section, and pressing the brakepad by being moved toward the brake pad through receiving rotationalpower from the planetary gear section.
 3. The parking brake apparatus ofclaim 2, wherein the pair of pressing units individually receive powerfrom the plurality of motor sections, respectively.
 4. The parking brakeapparatus of claim 3, wherein any one of the pair of pressing unitsreceives power by being connected with some of the plurality of motorsections, and wherein the other one of the pair of pressing unitsreceives power by being connected with the other some of the pluralityof motor sections.
 5. The parking brake apparatus of claim 3, whereinthe load transmission unit includes a pair of ring gear sections,wherein each of the pair of ring gear sections is rotatable by beingmeshed with the planetary gear section, and wherein the pair of ringgear sections are directly or indirectly meshed with each other.
 6. Theparking brake apparatus of claim 5, wherein each of the pair of ringgear sections comprises: a ring gear inner part formed with an internalgear portion on an inner circumferential surface thereof to be meshedwith the planetary gear section; and a ring gear outer part coupled toan outer surface of the ring gear inner part, and formed with anexternal gear portion on an outer circumferential surface thereof to bemeshed with the other ring gear section neighboring thereon.
 7. Theparking brake apparatus of claim 6, wherein the ring gear inner part andthe ring gear outer part are integrally formed.
 8. The parking brakeapparatus of claim 6, wherein the ring gear inner part projects moretoward the sun gear section than the ring gear outer part, and surroundsthe sun gear section and the planetary gear section.
 9. The parkingbrake apparatus of claim 2, wherein the carrier section isspline-coupled to the piston section.
 10. The parking brake apparatus ofclaim 9, wherein the piston section receives rotational power from thecarrier section, and is linearly reciprocated relative to the brake paddepending on a rotating direction of the carrier section.
 11. Theparking brake apparatus of claim 2, wherein the sun gear section isdynamically connected to the driving unit through a connection gearsection.
 12. The parking brake apparatus of claim 11, wherein the sungear section comprises: a sun gear connection body coupled to theconnection gear section; and a sun gear formed on the sun gearconnection body, having a rotation center that is concentric with arotation center of the connection gear section, and meshed with theplanetary gear section.